Many foods naturally contain molecules of sugar; fruit contains fructose and milk contains lactose. The human body uses the simple sugar glucose as the main source of fuel for the cells. Lactose consists of a glucose molecule bound to another sugar molecule known as galactose. In order to absorb the sugar for cells to use, your body must break it down into the two simple sugar molecules. Some people lack the enzyme needed to break down lactose which leads to a medical condition known as lactose intolerance. Doctors can perform lactose testing to diagnose lactose intolerance.
Lactose Intolerance
Lactose intolerance affects approximately 30 to 50 million people in the United States, according to Ohio State University Medical Center. The condition usually develops over time as your body gradually decreases the amount of lactase -- the enzyme produced by the cells lining the small intestine that breaks down lactose -- it produces. A primary lactase deficiency describes the condition when it occurs due to a gene inherited from a parent. Secondary lactase deficiency describes a lack of lactase enzyme due to injuries to the small intestine caused by another disease such as Crohn's disease or celiac disease.
Symptoms
Lactose intolerance causes symptoms that typically appear 30 minutes to two hours after you consume milk or other dairy products. When the normal process of digestion fails to break down the lactose in the small intestine, the sugar continues through the digestive tract. In the large intestine bacteria try to break it down causing digestive disturbances such as excessive gas, bloating, abdominal pain and diarrhea. Because these symptoms can occur as a result of many digestive conditions, including irritable bowel syndrome, doctors must perform lactose testing to get a definitive diagnosis.
Hydrogen Breath Test
Doctors routinely perform a lactose test known as the hydrogen breath test. To begin the test the technician will ask you to blow up a balloon-like bag. This provides a baseline for the amount of hydrogen in your breath. Normally your breath contains very little hydrogen. Then you need to drink a liquid that contains high levels of lactose. You must provide breath samples every 15 minutes for two hours to determine the amount of hydrogen following the ingestion of lactose. If your body cannot break down the lactose the bacteria in the large intestine ferments the lactose producing gases including hydrogen that eventually gets exhaled. Increased levels of hydrogen in the breath test indicate lactose intolerance.
Lactose Tolerance Test
In addition to the hydrogen breath test your doctor may order a lactose tolerance test. To perform this test you must provide a blood sample two hours after drinking the lactose liquid. The laboratory will measure the amount of glucose in your blood. If your body properly digests the lactose, your blood glucose level increases. If your glucose level fails to increase your body did not digest and absorb the lactose, indicating lactose intolerance.
Stool Acidity Test
Doctors may find it difficult to perform a hydrogen breath test or lactose tolerance test on infants and children. To determine if they suffer from lactose intolerance, the doctor can order a stool acidity test. Undigested lactose continues through the digestive tract to the large intestine. There bacteria attempt to break it down through the process of fermentation. This process produces acids, including lactic acid, that get excreted with the stool. A stool acidity test detects a higher than normal acid content that occurs as a result of lactose intolerance.
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